Method for producing hides with the aid of mold tryptases



Patented May 9, 1939 PAT E NT OFFICE METHOD FOR PRODUCING THE AID OF MOLD TRYPTASES Otto Riihm, Darmstadt, Germany- No Drawing. Application January 30,. 1937, Se-

rial 1936 28 Claims.

The invention relates to preparing hides or skins for tanning, and more particularly to subjecting such hides or skins for depilating and/or bating purposes to neutral, weakly' acid or weakly basic solutions containing tryptases formed from molds, in the presence of one or more activators, such tryptases being effective in the absence of enzymes of any other type. The present application is a continuation-in- 10. part of my United States application Serial No. 70,890 filed March 25, 1936, now Patent No. 2,132,579, issued October 11, 1938, and of my United States application Serial No. 104,147 filed October 5, 1936, now Patent No. 2,139,209, issued December 6, 1938, the entire disclosure of which is hereby incorporated by reference as part of the disclosure of the present application.

In my United States applications Serial No. 70,890 and Serial No. 104,147, there are described methods for depilating and bating skins and hides with the aid of mold tryptases, especially the hyphomycetes tryptases produced by Aspergillus varieties and using an alkaline, neutral and weakly acid solution, and wherein various accelerators or compounds favoring the enzymatic action are added, e. g., sodium bisulphite, or sodium thiosulphate. Furthermore, compounds which contain one or more hydroxyl groups such as grape sugar, glycerin, or lactates 0 can be used. These additions may also be used in combination. In addition, ammonium salts, or ammonium hydroxide may be used conjointly, these being among others, suitable for retarding the occurrence of decay phenomena, or alkaline reacting salts may be added, or they may be used during the swelling or non-swelling steps, .such salts being sodium carbonate, sodium bicarbonate, borax and the sodium phosphates.

It has also been found that the method intended for producing dehaired hides intended for tanning and involving the use of the aforesaid mold tryptases may be further improved if suitable oxidizing agents areused as addition agents, particularly salts of nitric acid, e. g., an alkali nitrate, and salts of nitrous acid, e. g., analkali nitrite. Whereas in the processes described in the aforementioned applications the conjoint use of ammonium compounds (among others) proved advantageous owing to their decay inhibiting action, sodium nitrate and sodium nitrite alone, without addition of ammonia compounds, act bactericidally to a higher degree than is the case of the activators described inthe above mentioned applications which use an addition of ammonium compounds. Inasmuch as their acti- In Germany February 7,

vatingaction isv also very good this makes for a further simplification and improvementv of the.

process. a

It has already been proposed to use. nitrates coniointly in the enzymatic treatment, of skins, 5 but-only in such a manner that the activating action comes into play in conjunction with a swelling action of the salts upon the skin. The action of these neutral salts in this case may be classified according to the Hofmeister series. In accordance therewith, a chlorate reacts stronger than a nitrate. But it appears that the mold type of mold tryptase is far less activated by chlorates, in fact it is even rather more inhibited in itsaction than by nitrates. The process specifically described in the present application therefore deals with an entirely specific action which is quite typical of mold tryptase and which has not hitherto been described in this connection.

Sodium nitrate or sodiumnitrite may also paitly be replaced by other salts, e. g., common sal Among other oxidizing agents, hydrogen peroxide, sodium peroxide with or without addition of'common salt, sodium perborate or other per" compounds (except perchlorate) are suitable. Those that are not suitable are for example, oxidizing agents which produce undesirable side reactions such as bichromate which tends towards an excessive tanning action, or permanganate which produces coloration, or compounds of the type of p'erchlorates.

In order further to increase the enzymatic action, it has been found very desirable to use the mold tryptase enzymes in conjunction with their activators at a somewhat elevated temperature, that is, at about 25-30 C. This is especially im portant for difflcultly dehairable hides or skins.

The great practical significance of the bactericidally acting activators is demonstrated by the fact that itis possible through their agency to obtain the eiiect of the old and well known sweating process without its disadvantages, side reactions, etc. since the production of decay bacteria and consequently damaging of the a skin substance need no longer be feared. In the'ordinary sweating process, decay bacteria were deliberately relied upon, but they could easily become dominant since their growth could not be positivelycontrolled; in the present process however, only a very definite quantity of enzyme is utilized which is sufflcient without the presence of decay bacteria, to produce depilation in a short time, i. e;, after 1-2 days. The ordinary sweating process on the other hand requires up to 8 days and even after such time the depliation of the skins frequently involves additional appreciable difliculties. I

Thus, for example, the hides or skins may be coated with a solution of mold tryptase and sodium nitrite or they may be drawn through this solution, allowed to lie 2-3 hours, until the solution is taken up by the skins and then allowed to hang in a moist chamber at a temperature of about 30 C. After 1-2 days they may in general be readily depilated free from basic hair. The hair loosening action may if desired be further augmented by subsequently treating the skins,

prior to dehairing, for 12 days with a weak soda or ammonia solution. In the case of sheep hides .it'is sometimes preferable to remove the wool from the hides prior to the soda treatment and then first place them in the soda solution so as to protect the wool from the alkaline action of the soda solution. This prevents a portion of the wool grease being taken up by the soda solution and thereby becoming uselessly lost. The wool which has not come in contact with alkalies and soda solution is in this case of the same high quality as shorn' wool. The yield is even better than in the case of shorn wool since the wool fibres areobt'ained in long lengths.

If in the processes described in the aforementioned applications the operation is carried on at elevated temperatures in order to assist the enzymatic action, then decay may occur before the skins are ready for dehairing. The addition of ammonium compounds will appreciably reorder to acidify the hides or skins, boric acid,

lactic acid, or bisulphite may be used and in order to render them alkaline,-alkaline reacting salts like soda or sodium bicarbonate may beused.

Furthermore, in the case of certain hides or skins and for those derived from special sources, the alkali nitrate or alkali nitrite process may be combined in every way withthe other activators recited in this application or with the processes described in the above mentioned applications and the procedure carried out in weakly acid to weakly alkaline solution.

Thus, dry hides may be softened with about 2% sodium sulphite, if desired, with the addition of soda, and the thus softened hides then treated with the mold tryptase solution with addition of sodium nitrite, sodium nitrate, etc.

This procedure, in which the hides are pretreated with reducing acting compounds and then subjected to the action. of mold tryptase with addition of oxidizing substances such as sodium nitrate or sodium nitrite, etc. has the great advantage that the depilating action of the mold tryptase is greatly facilitated thereby.

However, hides or skins softened with water may be treated with mold tryptase with addition of sodium'nitrite and sodium lactate and then depilated prior to or after the sodav treatment.

Whereasformerly the general viewpoint was Examples 1 (1) 100 kgs. of goat hides, softened as usual, are kneaded for one hour in a vat with a solution of: Mold tryptase from Aspergillus flaous kg 1 Sodium nitrite kg 1 Water at 30 C liters 100 and then allowed to remain over night in a vat. After 24 hours there is added a solution of: Calcined soda kgs 6 Water at 30 C .liters 300 In order to effect a uniform action of the soda solution, stirring isicarried on for 10 minutes. After two days they may be depilated free from basic hair. The dehaired hides, after being 25 cleaned, are ready for pickling or tanning without subsequent hating.

(2) 100 kgs. of goathides, softened as usual.

are kneaded in a vat for one hour with a solution of: Mold tryptase from Asper gillus wentii kgs 1.5 Sodium nitrate kgs 1.0 Water of C liters 100 and then worked up further as indicated in Example 1.

v(3) .100 kgs. of cattle hides, softened as usual, are superficially limed with the following solution or drawn through the same: 0 Mold tryptase from Aspergillus efiusus kg 1 Hydrogen peroxide 30% liter 1 Water liters 10 After lying for one day at about 25 C. the skins are then treated for two days with a solution of:

Calcined soda kgs 10 Water liters 500 After this time they may be depilated free from basic hair. The skins are washed out and may after the usual cleaning be subjected to dyeing for producing sole leather.

(4) 40 kgs. of sheep hides are softened with;

Water liters 400 Sodium sulphite kg :1 Calcined soda. kg .1 and after the softening is finished and the hides have been allowed to drip, they are bated with a solution of: I Mold tryptase from Aspergillus parasiticus k .6 Sodium perborate kg 1.0 Water liters 15.0 The hides are allowed-to lie for two days at a temperature of 25-30 C. or are hung up in a moist warm chamber, then freed of wool,- and subsequently treated with a solution of: 'Calclned soda kgs 10.0 7 Water liters 500.0

After the usual cleaning the dehaired hides are ready for pickling or tanning without requiring are kneaded for one hour in a vat with a solution of.

Thereupon the hides are allowed to remain 24 hours in the vat and next morning there is added a solution of:

calcined soda kgs 6 Water at C liters 300 The /solution is stirred for 10 minutes in order to e'ifect a uniform action of the soda solution; after two days the hides may be depilated free from basic hair.

(6) Kid hides normally batedwith lime arsenic, are, after depilating, washed with soft water for about two hours and then 100 kg. of hide weight is bated with;

Mold tryptase from Aspergillus flavus kg .35 Ammonium sulphate kg .4 Sodium nitrite kg .4 Water at 2530 C liters 300 type are added to the mold tryptase solution per se. This favorable action was all the more surprising when it is considered that no advantages could be expected from a simultaneous mixture of oxidizing and reducing agents as accelerators.

The skins, after ordinary softening in water,

may be kneadedin a vat for onehour with a solution of mold tryptase, sodium sulphite and sodium nitrite, and can be depilated after a few days. In order to adjust the solution on the alkaline side, weak alkalies such as alkali carbonate, alkali bicarbonate, borax or sodium phosphate may be used in conjunction. Since damage to the skin substance is largely avoided by this method, the same is especiallysuited for such leather varieties as are sold by weight.

Hides or skins may be treated in the lime pit in a corresponding manner.

I The liming process is especially recommended for sheep skins, in order to secure a wool quality of the same value as shorn wool. The sheep skins are therefore limed on the fleshy side with a solution of mold tryptase, sodium sulphite and sodium nitrite or sodium nitrate, if desired, with the addition of soda, and then de-w'ooled after 1 -to 2 days. After being de-wooled they may be after-treated with a weak soda solution. It has been'rfound that by this process a greater yield 'ofjwool and a more valuable wool is obtained than with the liming process using lime and sodium sulphide or similarv sulphide containing products. In working goat skins up into glove leather, a

- liming, pit. procedure has been found suitable wherein the skins are limed with the mold tryp;

' tase solution, with addition of sodium sulphite or asimilar sulphurcontaining compound and The hides, after the usual ,cleaning may be pickled or tanned without requiring subsequent bating.

sodium nitrite or other suitable oxidizing agent, if desired, with the addition of soda, and after being allowed to remain in the pit for four hours they are covered with water. After 3 to 4 days they can be depilated and if desired, after-treated again for several days with a weak soda solution.

This method may furthermore also be combined with the method described in my United States applications Serial No. 70,890 and Serial For example, hides or skins may be pre-treated with wetting agents which treatment is then first to be followed, by treatment with mold tryptase solution and the above mentioned additions. But it is also possible to add the wetting agents to the solution per se.

Furthermore, compounds containing hydroxyl groups such as alcohols, aliphatic oxy-acids, carbohydrates, phenols, naphthols, may be added to the mold tryptase solution containing sodium nitrite, sodium nitrate or similar oxidizing agents as well as sodium sulphite or similar sulphurcontaining compounds. For certain skins and hides and for certain varieties of leather, the

' skins or hides may be subjected to a swelling or non-swelling alkaline before or after treatment.

In order -to adjust the mold tryptase solution to neutral or acid condition;- weak acids or acid salts may be used, such, for example, as boric acid or sodium bisulphite. For de-swelling the .swelled skins or hides, an addition of ammonium salts is also suitable.

The skins or hides may also be depilated after the alkaline pre-treatment. In this case the mold tryptase solution and its additions such as sodium nitrite and sodium sulphite or sodium bisulphite or ammonium salts acts as a bating agent.

It has already been proposed to activate vegetable or animal proteases by means of thio acids or their salts or even by other oxygen containing compounds containing sulphur in bior quadri-valent form and to use the enzyme solutions for depilating and bating calf skins. with the aid of papain in admixture with mold tryptase for depilating and bating. Finally, a process tase, particularly the Aspergillus varieties. Likewise it could not be deduced from these proposals that without using other enzymes with mold tryptases in combination with the additions herein claimed that particular advantages would be secured in depilating and bating. The possibility of operation with mold tryptase as the sole enzyme is also advantageous because of the fact that this enzyme is easy to produce in any quantity desired and that its action is always easy to-control.

Example 1a 100 kgs. of cattle hides, softened as usual, are kneaded in a vat for one hour with a solution of Mold tryptase from .ispe'rgz'llus flavus kgs 1.5

. the liming solution,

After a total of two days the hides are depilated, and then worked up without subsequent bating, that is, defleshed or shorn, scraped or smoothed, washed out, and tanned. The action of the mold tryptase solution is effected at a pH of 9 to 10.

. Example 2a Salted or dried sheep skins are softened as usual. After the softening is completed, the skins are allowed to drip for one hour whereupon they are limed on the fleshy side with a solution of:

Parts Mold tryptase from Aspergillus flavus 3.0 Sodium sulphite .4 Sodium nitrite Water 10.

and allowed to.rcmain, folded up, for 1 to 2 days. After this tiine the skins are de-Wooled and aftertreated per 100 kg. of hide weight) for two days with a solution of Water lite1's 300 Calcined soda kgs 6 they are then defleshed, cut, smoothed, washed out and pickled or tanned without subsequent hating. The action of the mold tryptase solution is effected at pH 7.

Example 3a The procedure is the same as in Example 211. However, .2 kg. calcined'soda are used along with The action of the mold tryptase solution is effected at a pH of 9.

" Example 4a The procedure is the same as in Example 2a. However, along with-the liming solution there is limed in the pit with a solution of Mold tryptase from Aspergillus flavus kgs 1.5 Sodium nitrite kg.. .5v Sodium sulphite.. kg .5 Calcined soda kgs 6.0 Olein alcohol sulphonate kg .2 Water liters 40 After three days of pit liming the skins are depilated, defleshed,

fected at pH 9 to 10. 1

Example 6a Goat skins (per 100 kgs. of dry weight) are softened with: Water liters 500 Lauryl alcohol sulphonate. kg .3

After the softening is finished, the skins are allowed to drip for an hour and are then limed on the fleshy side with a solution of 4 Parts Mold tryptase from Aspergillus flavus 3.0 Sodium sulphite 1.0 Sodium nitrite 1.0 Soda [.2 Phenol .2

smoothed, washed out, and I pickled or tanned without subsequent bating.

The action of the mold tryptase solution is ef- The limed skins are allowed to rest for 4 hours and are then covered with so much water in the pit that the skins are completely immersed. After days they are depilated and then after-treated,

per 1000 kgs. of hide weight for 3 days with: Water liters 400 Calcined soda kgs 5 When removed from this solution the skins are defleshed, washed out, smoothed, rinsed, and

pickled or tanned without subsequent bating. The

action of the mold tryptase solution is efiected at Example 7a The procedure is the same as in Example 6a. In lieu of sodium sulphite however, the same amount of sodium thiosulphate is used. The action of the mold tryptase. solution. is effected at pH 9.

Example 8a Ordinary lamb skins, limed with lime-arsenic,

are, after being de-wooled, washed with soft water for about 2 hours and then bated per 100 kgs. of

.hide weight with:

Mold tryptase kg .35 Sodium bisulphite kg .5 Sodium nitrite kg .5 Ammonium sulphate kg .5

Water at a temperature of 25-30 C liters 30 together with at least one oxidizing agent of the I class consisting of alkali nitrates, alkali nitrites,

alkali percarbonates,- alkali peroxides, and hydrogen peroxide in weakly acid to weakly alkaline aqueous solution. 1

2. A method for producing ready-to-tan hides or skins which comprises subjecting hides or skins for depilating and hating purposes to enzymes consisting substantially of mold tryptases together with at least one oxidizing agent of the class consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides, and hydrogen peroxide in weakly acid to weakly alkaline aqueous solution, and adding to the solution of enzymes and oxidizing agents at least one reducing oxygen-containing sulphur compound selected from a group consisting of alkali sulphites, alkali bisulphites and alkali thiosulphates.

3. A method according to claim 1, wherein the hides or skins are subjected to a pre-treatment consisting of soaking in water, then treated according to claim 1 andthereafter dehaired.

4. A method according to claim 1, wherein the hides or skins are subjected to a pre-treatment consisting of soaking in an aqueous solution of at least one reducing oxygen-containing compound of sulphur selected from a group consisting of alkali 'sulphites, alkali bisulphites and alkali thicsulphates, then treated according to claim 1 and thereafter dehaired.

5. A method according to claim 1, wherein the hides or skins are subjected to a pre-treatment consisting of soaking in a weak non-swelling al-' kaline aqueous solution, then treated according I to-claim 1 and thereafter dehaired.

6. A method according to claim 1, wherein the hides or skins are subjected to a pre-treatment consisting of plumping in a strong alkaline solution, then treated according to claim 1, and thereafter dehaired.

7. A method according to claim 1, wherein the hides or skins are subjected to a pro-treatment consisting of plumping in a strong alkaline solution, then dehaired and thereafter treated according to claim 1.

8. A method according to claim 1, wherein the hides or skins are after-treated with an aqueous alkaline solution and then dehaired.

9. A method according to claim 1, wherein the hides or skins are dehaired' after the treatment with the enzyme solution and then treated with an alkaline solution.

10. A method for producing ready-to-tan hides or skins consisting of soaking hides or skins in water, then treating them with an aqueous solution containing tryptases from an Aspergillus variety together with a member of the group consisting of alkali nitrite, alkali nitrates, alkali percarbonates, alkali perborates, alkali peroxides and hydrogen peroxide, subjecting them to an aqueous solution of an alkali carbonate and dehairing them.

11. A method forproducing ready-to-tan hides or skins consisting of soaking hides or skins in water, then treating them with (1) an aqueous solution containing tryptases from an Aspergillus variety together with a member of the group consisting of alkali nitrites, alkali nitrates, alkali percarbonatesalkali perborates, alkali peroxides and hydrogen peroxide, and 2) grape sugar, subjecting them to an aqueous solution of an alkali carbonate and dehairing them. I

12. A method for producing ready-to-tan hides or skins consisting of soaking hides or skins in an aqueous solution of an alkali sulphite, then treating them with an aqueous solution containing tryptase from an Aspergillus variety together with an alkali perborate, subjecting them to an aqueous solution of an alkali carbonate and dehairing them.

13. A method for producing ready-to-tan hides or skins consisting of liming hides or skins, de

hairing them and then treating them with an' aqueous solution containing tryptase from an As-.

pergillus variety together with an alkali nitrite and an ammonium salt. v

14. A method for producing ready-to-tan hides or skins consisting of soaking hides or skins in water, then treating them withlan aqueous solution containing tryptase from an Aspergillus variety together with an alkali nitrite and an alkali sulphite anddehairing them.

15. A method for producing ready-to-tan hides I variety together with an alkali nitrite and an alkali sulphite, subjecting them to an aqueous solution 01 an alkali carbonate and dehairing them.-

1'7. A method for producing ready-to-tan hides or skins consisting of soaking hides or skins in water, then treating them with an aqueousfsolation containing tryptase from an Aspergillus variety together with an alkali nitrite and.

alkali sulphite and an alkali carbonate, subjecting them to an aqueous solution of analkali carbonate and dehairing them.

18. A method for producing ready-to-tan hides or skins consisting of liming hides or skins, dehairing them and then treating them with an aqueous solution containing tryptase from an Aspergillus variety together with an alkali nitrite, an alkali sulphite and an ammonium salt.

19. A method for producing ready-to-tan hides or skins which comprises subjecting hides or skins for depilating and bating purposes to enzymes consisting substantially of mold tryptases together with at least one oxidizing agent of the class consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides, and hydrogen peroxide in weakly acid to weakly alkaline aqueous solution, and adding to the solution an alkaline reacting salt selected from a group consisting of alkali carbonates, alkali bicarbonates,

alkali perborates and alkali phosphates.

20. A method for producing ready-to-tan hides or skins which comprises subjecting hides or skins for depilating and bating purposes to enzymes consisting substantially of mold tryptases together. with at least one oxidizing agent of the class consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides, and hydrogen peroxide in weakly acid to weakly alkaline aqueous solution, and adding to the solution and ammonium compound.

21. A method for producing ready-to-tan hides or skins which comprises subjecting hides or skins for depilating and bating purposes to enzymes consisting substantially of mold tryptases together with at least one oxidizing agent of' the class consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides, and hydrogen peroxide in weakly acid to weakly alkaline aqueous solution, and adding to the solution a neutral alkali salt. I

for depilating and bating purposes to enzymes consisting substantially of mold tryptases together with at least one oxidizing agent of the class consisting of alkali nitrates, alkali nitrites, alkali percarbonates, alkali peroxides, and. hydrogen peroxide in weakly acid to weakly alkaline aqueous solution, and adding to the solution an organic compound containing one hydroxyl group selected from a class consisting of lactic acid and lactates.

23. A method for producing ready-to-tan hides or skins which comprises subjecting hides or skins fordepilating and bating purposes to enzymes consisting substantially of mold tryptases together with at least one oxidizing agent of the class consisting of alkali nitrates, alkalinitrites,

' alkali percarbonates, alkali peroxides, and hydrogen peroxide in weakly acid to weakly alkaline aqueous solution, and adding to the solution an organic compound containing a number of hydroxyl groups selected from a class consisting of grape sugar and glycerine.

24. ,A method according to claim 2, wherein an alkaline reacting salt selected from a group consisting of alkali carbonates, alkali bicarbonates, alkali perboratesandalkali phosphates, is added to the solution of the enzymes and the oxidizing and reducing agents.

25'. A method according to claim 2, wherein an.

ammonium salt is addedtothesolution'oI the enzymes and the oxidizing and reducing agents.

26. A method according to claim 2, wherein a neutral alkali salt is added to the solution of the enzymes and the oxidizing and reducing 5 agents.

27. A method according to claim 2, wherein a wetting agent is added to the solution of the enzymes and the oxidizing and reducing agents. 28. A method according to claim 2, wherein an organic compound containing one hydroxvl group selected from a class consisting of grape sugar and glycerine is added to the solution of the enzymes and the oxidizing and reducing agents. 

